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Published on: February 27, 2018
The impact of increasing femoral offset and stem anteversion on postoperative dislocation in bipolar hemiarthroplasty
Takeshi Shoji1, Tadashi Inoue2, Yuichi Kato2
1Department of Artificial Joints and Biomaterials, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Insights
Optimizing femoral offset and stem anteversion in bipolar hemiarthroplasty improves range of motion. Surgeons should consider these factors, as they significantly impact flexion, internal, and external rotation.
Area of Science:
- Orthopedic surgery
- Biomechanics
- Implant design
Background:
- Femoral offset and stem anteversion are critical factors influencing dislocation risk after bipolar hemiarthroplasty.
- The precise impact of these parameters, individually and combined, on dislocation remains incompletely understood.
Purpose of the Study:
- To investigate the relationship between femoral offset, stem anteversion, and range of motion in bipolar hemiarthroplasty.
- To quantify the effects of varying femoral offset and stem anteversion on hip joint kinematics.
Main Methods:
- Utilized CT data from 61 patients undergoing bipolar hemiarthroplasty.
- Performed 3D dynamic motion analysis with a modular implant allowing independent adjustment of femoral offset and stem anteversion.
- Evaluated impingement patterns and range of motion using specialized software.
Main Results:
- Higher femoral offset and stem anteversion correlated with increased flexion and internal rotation.
- Increased femoral offset had a greater impact on flexion range than stem anteversion.
- Stem anteversion significantly influenced internal rotation, particularly with lower femoral anteversion.
- Higher stem anteversion decreased external rotation, while higher femoral offset increased it.
Conclusions:
- Both femoral offset and stem anteversion substantially influence range of motion in flexion, internal, and external rotation.
- These parameters are not independent and interact in complex ways.
- Surgeons should prioritize maintaining appropriate femoral/anterior offset during bipolar hemiarthroplasty to optimize outcomes.
Background:
Femoral offset and anteversion have been reported to affect the incidence of dislocation following bipolar hemiarthroplasty, although the magnitudes of contributions of the femoral offset and stem anteversion on dislocation, both singly and in combination is not fully understood.
Methods:
Using the CT data of 61 patients (61 hips), including 30 male and 31 female who underwent bipolar hemiarthroplasty, three-dimensional dynamic motion analysis was performed using a modular implant that enabled adjustment of femoral offset and stem anteversion independently. The pattern of impingement and relationship between femoral offset/stem anteversion and range of motion were evaluated using the software.
Findings:
We found that a higher femoral offset and stem anteversion correlate with a greater range of motion of flexion and internal rotation. Furthermore, an increased femoral offset has a great effect on increasing range of motion of flexion than stem anteversion, and increased both femoral offset and stem anteversion have fewer effect on the flexion, whereas increasing stem anteversion has a great impact on internal rotation than offset, especially in the case with lower femoral anteversion. However, a higher stem anteversion decrease the range of motion of external rotation, whereas a higher femoral offset leads to an increased range of motion of external rotation.
Interpretation:
We demonstrated that both a higher femoral offset and stem anteversion substantially affected the range of motion in flexion, internal rotation and external rotation. However, these are not independent, but rather mutually confounding, the surgeons should consider retaining femoral/anterior offset in bipolar hemiarthroplasty.
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